Coating non-planar surfaces



Sept. 17, 1968 E. c. YACKEL ET AL 3,402,087

COATING NON-PLANAR SURFACES Filed Dec. 25, 1964 F/GJ STRIPPED RADIATION- SENSITIVE LAYER BEING COATED 0N PERMANENT SUPPORT HE M/S PHE I?! CA L SUPPORT L IOU/D MED/UM RAD/A T/D/V-SE/VS/ T/ V5 1.4 YER FIG, 3

HE M15 PHE RICA L SUPPDR T EDWARD 6. YACKEL DONALD P. FOSTER INVENTORS BY %M/M ATT'DEWEYD AGENT United States ABSTRACT OF THE DISCLOSURE This invention is primarily concerned with the application of uniform photosensitive coatings to non-planar surfaces wherein the coating is preformed on a planar support, stripped from the support, floated on a liquid medium capable of swelling the coating, and finally contacted with the non-planar surface.

The present invention is related to a method for the preparation of coatings on non-planar, and more particularly convex or concave surfaces having a high degree of uniformity.

A variety of ways have been proposed for the coating of non-planar surfaces with photosensitive compositions. Thus, coatings on non-planar surfaces have been produced by dipping a chilled non-planar support into a melted photosensitive emulsion or 'by spraying the photosensitive composition in liquid form onto the non-planar surface. These techniques have not found use in applications which require a high degree of photographic quality since they result in variations in the thickness of the coating, contain air bubbles in the coating and have other deficiencies. The method of coating a thermoplastic film with a photosensitive material and then moldin the film to the desired shape is also known in the art. However, this method has the disadvantage of having to subject the photosensitive material to the high temperatures and pressures of the molding steps, which may adversely affect the photosensitive composition. Furthermore, the film may be stretched during the molding operation and thus cause a variation in the thickness of the photosensitive coating. Additionally, the resulting surface of the photosensitive coating is only as smooth as the surface of the mold. Highly polished molds are not only expensive, but, are easily marred when frequently used.

It is, therefore, an object of the present invention to provide a method for the coating of non-planar surfaces and particularly convex surfaces with radiation-sensitive materials. It is another object of the present invention to provide a method for obtaining uniform and smooth radiation-sensitive coatings on non-planar surfaces. Other objects will become apparent hereinafter.

In accordance with the present invention, uniform and smooth coatings of radiation-sensitive compositions are obtained on non-planar, and particularly convex surfaces by a process which comprises depositing a radiationsensitive composition of the desired thickness on a temporary support, stripping the resulting coating from the temporary support, floating the stripped coating on a liquid medium capable of swelling the coating, the stripped surface of the coating being in contact with the liquid medium, over the submerged surface to be coated, contacting the non-planar surface with the radiation-sensitive coating at a temperature below the break temperature preferably in the range from about 1 to about F. below the break temperature, and thereafter, if desired, hardening the radiation-sensitive composition on the non-planar surface. By break temperature is meant, that temperature at which a film of the radiation-sensitive composition, heated in contact with the said liquid medium breaks when applied to the non-planar surface.

atent ice By radiation-sensitive composition is meant, a composition containing a material which has inherent radationsensitivity or a radiation-sensitive agent dispersed in a carrier capable of swelling in a suitable liquid medium. In another embodiment of our invention, a photosensitive element comprising at least one hydrophilic layer and at least one light-sensitive layer is coated on the temporary support and then stripped from the temporary support and transferred to the non-planar surface by the steps described above.

A wide variety of radiation-sensitive compositions are used to advantage according to our invention, including any of the known hydrophilic colloid silver halide emulsions of the developing-out type or of the print-out type; nonsilver print-out compositions (such as are described by Poznan Towarz, Pryjaciol, Nauk, Wydzial Mat- Przyrod, Prace Komis, Mat-Przyrod 7, No. 9, 7996 (1959), Sagura et al., U.S. Ser. No. 227,561, filed Oct. 1, 1962, Rauner et al., U.S. Ser. No. 266,691, filed Feb. 1, 1963, etc.); photoresist compositions (e.g., light sensitive polymers such as polymers containing an a,fi-unsaturated carbonyl group including those described in patents such as Minsk et al., U.S. 2,610,120 issued Sept. 9, 1952, Robertson et al., U.S. 2,732,301 issued Jan. 24, 1956, etc., polymers containing an azide group, such as those described by Merrill et al. in U.S. 3,002,003 issued Sept. 26, 1961, and others; polymers containing a quaternized pyridine group having an unsaturated group attached to the carbon atom in the two position, such as are described by Leubner et al., U.S. 2,811,510 issued Oct. 29, 1957, etc.) xerographic compositions (such as those described by Middleton, U.S. 3,120,006 issued Feb. 11, 1964, Greig 3,052,539 issued Sept. 4, 1962, etc.); etc.

The hydrophilic radiation-sensitive compositions of our invention are advantageously coated directly on the temporary support or base. Hydrophobic radiation-sensitive compositions can be coated directly on the temporary support provided that an appropriate liquid swelling agent for the composition such as a non-polar solvent or other organic solvent is utilized. Examples of non-polar solvents used to advantages as swelling agents for hydrophobic colloids are, acetone, 2-ethoxyethanol, benzene, toluene, etc. The non-polar solvent selected will be dependent upon the particular hydrophobic colloid used in the radiation-sensitive layer.

The sensitive compositions most generally employed in the process of the present invention comprise a watersoluble or water-permeable colloid, such as gelatin, albumin, gum arabic, hydrolyzed cellulose acetate, or polyvinyl alcohol in which there is dispersed a sensitive component, such as a silver halide, a light sensitive iron salt, diazonium compound, or any of the other light-sensitive materials used in photography. Addenda known to those skilled in the art such as color formers, dye intermediates, filter dyes, sensitizing dyes, etc., may be present in the photo-sensitive composition. The preferred compositions of the present invention are, however, silver halide dispersions in gelatin coated as a single layer or as a multilayer element, such as is used for color photography. Depending on the specific nature of the gelatin employed in these composiitons, coatings of these compositions are applied to the non-planar and particularly convex surfaces using water as the liquid medium at temperatures of about 65 to F. and preferably at temperatures of 79 to 82 F.

The temperature at which the stripped coating of the photosensitive composition is applied to the non-planar, convex or concave surface is extremely important. If the break temperature is exceeded, obviously the coating will break or at least contain tears. If the temperature employed is too far below the break temperature, the photosensitive coating will not drape properly over the non-planar surface and result in folds and overlaps. The optimum coating temperature is readily established by experimentally determining the break temperature.

The coating is preferably applied so that the stripped surface of the coating, i.e., the surface which had contacted the temporary support from which the coating was stripped, contacts the liquid medium on which the coating floats. It is also advantageous to cut the coating either before or after stripping to dimensions that will result in covering the desired area of the non-planar surface, since this minimizes any overlaps and folds in the finished coating.

As indicated above, the photosensitive composition is first applied to a temporary fiat support to achieve the desired uniform thickness. Processes developed in the prior art for applying uniform photosensitive coatings to flat supports are well known and therefore need not be described here. Preferably, the coating is applied to a flexible film support, such as an unsubbed cellulose ester film, terephthalate film, polyester film, etc., from which the composition can be readily stripped.

The invention is further illustrated by the following examples.

EXAMPLE I An unhardened photosensitive silver halide emulsion was coated on the unsubbed side of cellulose triacetate film base to result in a coating containing 100 mg./ft. of silver chloride, 1,000 mg./ft. of gelatin and 100 rug/ft. of glycerol. Portions of the dry film were stripped from the base and placed on a still water surface, maintained at a temperature of 80 F. The coating was placed on the Water with the stripped surface in contact with the water. The gelatin film swelled rapidly in one to two minutes. A glass sphere was placed under the surface of the swollen gelatin film and slowly elevated so that the gelatin film draped itself over the surface of the sphere. A uniform coating over the convex portion of the sphere was obtained.

EXAMPLE II Following the procedure of Example I, a coating of the photosensitive composition was prepared. The resulting coated film base was then cut to cover the outer side of a glass hemisphere. The photosensitive coating was then placed on the water surface in the manner indicated in Example I, the water being maintained at a temperature of 80 F. and containing submerged therein the glass hemisphere corresponding to the size of the cut coating. The water was then drained from the container such that the photosensitive coating was draped over the outer side of the hemisphere. The coating uniformly covered the hemisphere without the formation of any folds.

The dried coating was flashed to light and brush developed with a composition comprising:

'Para-methylaminophenol sulfate g 3.0 Sodium sulfite, desiccated g 45.0 Hydroquinone g 12.0 Sodium carbonate H O g 80.0 Potassium bromide g 2.0 Water liter 1.

FIG. 1 shows a cross sectional view of temporary support 10 coated with radiation-sensitive stripping layer 11.

FIG. 2 shows a cross sectional view of stripped radiation-sensitive layer 11 being coated on permanent hemispherical support 12 by draining the liquid medium 13 on which layer 11 was floated in tank 14 through drain 15.

FIG. 3 shows hemispherical support 12 coated with radiation-sensitive layer 11.

In a similar manner concave surfaces are coated to advantage with a radiation-sensitive layer. For this purpose it is advantageous to provide a means for removing the liquid medium from the concave surface, such as for example by providing a small opening at the bottom of the concave surface for the liquid medium to drain when the tank is drained.

The techniques described above for coating single layers on non-planar surfaces are used to advantage in coating multilayer radiation-sensitive elements such as are used for color photography. As mentioned previously an unsubbed temporary support is used to advantage for these coatings so they can be readily stripped as a unit from the temporary support.

Our invention provides a technical advance in the coating of uniform and smooth radiation-sensitive layers on non-planar surfaces.

The invention has been described in detail with par ticular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined the appended claims.

We claim:

1. A process for coating non-planar surfaces with a radiation-sensitive composition which comprises depositing a radiation-sensitive composition of the desired thickness on a temporary planar support, stripping the resulting coating from the said temporary support, floating the stripped coating on a liquid medium capable of swelling the coating over a submerged non-planar surface, and contacting the non-planar surface with the the photosensitive coating at a temperature below the break temperature of the coating.

2. A process for coating non-planar surfaces with a photosensitive composition containing a light-sensitive agent dispersed in a hydrophilic colloid, which comprises depositing the photosensitive composition on a temporary planar support to the desired thickness, stripping the resulting coating in its unhardened state from the said support, floating the stripped coating on water over a submerged non-planar surface, and contacting the non-planar surface with the photosensitive coating at a temperature below the break temperature of the coating.

3. The process of claim 2, wherein the hydrophilic colloid is gelatin.

4. The process of claim 2, wherein the light-sensitive agent is a silver halide composition.

5. The process of claim 2, wherein the non-planar surface is contacted with the coating at a temperature of 65 to F.

6. The process of claim 2, wherein the photosensitive composition is deposited on a flexible support from which the coating is strippable.

7. The process of claim 2, wherein a sliver halide gelatin emulsion layer is contacted with a non-planar surface at a temperature of 79 to 82 F.

8. The process of claim 2, wherein the stripped coating is floated on water at a temperature of about 1 to about 20 F. below the break temperature of the said coating and then the floating coating is contacted with a submerged non-planar surface.

9. A process for coating non-planar surfaces with a photo-sensitive element comprising at least one hydrophilic colloid layer and at least one light-sensitive layer, said process comprising the steps:

(1) coating on a temporary planar support the hydrophilic colloid layer and at least one light-sensitive layer,

(2) stripping the said photosensitive element from the said temporary planar support,

(3) floating the stripped element on a liquid medium capable of swelling the said hydrophilic colloid layer of said element over a non-planar surface submerged in said liquid, and

(4) contacting the said non-planar surface with the said hydrophilic colloid layer of said element at a temperature below the break temperature of the said element.

10. A process for coating non-planar surfaces with a photosensitive element comprising at least one unhardened hydrophilic colloid layer and at least one lightsensitive layer, said process comprising the steps:

(1) coating on a temporary planar support the unhardened hydrophilic colloid layer and at least one light-sensitive layer,

(2) stripping the said photosensitive element from the said temporary planar support,

(3) floating the stripped element on a liquid medium capable of swelling the said unhardened hydrophilic colloid layer of said element over a non-planar surface submerged in said liquid,

(4) contacting the said non-planar surface with the said unhardened hydrophilic colloid layer of said element at a temperature below the break temperature of the said element, and

(5) hardening the said element on the said non-planar support.

References Cited UNITED STATES PATENTS 5/1961 Kerstetter et al. 313-34.6 4/1962 McKeirnan et a1. 156-307 X 

